Facilitates tag and attribute name processing

I didn't update the README yet, since I want to be sure you like the approach.

There's 2 new options: `tagNameProcessor` and `attrNameProcessor`. Both accept an Array of functions which are required to have the following signature:

```coffee
(name) ->
  processedName = process name
  return processedName
```

I also refactored the `normalizeTags` functionality to such a processor.
Let me know what you think, then I'll update the README.

Would it be a good idea to provide some of those processors out of the box? For instance `stripPrefix` and `toCamelCase` ? As I wrote, actually there _is_ one already: `normalizeTags`


see #115
see #114